Urban Planning Design Considerations for Better Water Quality, Bill Hunt NC State University
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This document discusses various studies and case studies related to the impacts of development on water quality. It summarizes that effective solutions require maintaining watershed hydrology through low impact development techniques like reducing impervious surfaces, incorporating bioretention areas, and maintaining wetlands and riparian buffers. A case study of the Carpenter Village development showed positive results from using clustered housing, narrow streets, integrated open space and bioretention to minimize impacts on water quality.
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Urban Planning Design Considerations for Better Water Quality, Bill Hunt NC State University
- 1. Designing to Protect Water Quality
- 2. Belle Hall Study: Sprawl
- 3. Belle Hall Study: Cluster
- 4. Belle Hall Study: Results
- 5. Impacts are related to more than just imperviousness . . . We need to try and maintain watershed hydrology
- 7. Surface Hydrology by the Numbers Source: Center for Watershed Protection, 1996 Parameter ParkingLot Meadow Curve Number 98 58 Runoff Coefficient 0.95 0.06 Time of Concentration (minutes) 4.8 14.4 Peak: 2 yr, 24 hr., CFS 4.3 0.4 Volume, 1”, CFT 3450 218 Velocity, 2 yr, FT/Sec 8 1.8 Change 1.6 Times More 15 Times More 3 Times Less 10 Times Higher 15 Times More 4 Times Faster
- 10. Carpenter Village Project Partners: WW Partners Ferrell Land Dev Co. Town of Cary NC Cooperative Ext. Funding Agencies: NC DENR - DWQ 319 NC DENR - DLQ
- 11. Monitoring Design Below Treatment Basin Above Control Basin Below Carpenter Village
- 12. Annual Loads at Carpenter Annual Loads at Carpenter 0 5 10 15 20 25 30 35 40 Load(kg/ha) Clearing Building TP TN NO3 NH3
- 13. Annual Loads at Carpenter Annual Loads at Carpenter 0 5000 10000 15000 20000 25000 Load(kg/ha) Clearing Building TSS
- 14. Rainfall vs. Runoff Rainfall vs Runoff 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Runoff/rainfall Clearing Building Wooded Runoff
- 15. Cooperators and Participants NCSU School of Design Extension Programs Design Research Laboratory NCSU Water Quality Group NC Dept of Health, Shellfish Sanitation Program Duke Marine Laboratory UNC Sea Grant NCDENR Division of Water Quality 319 Program Wetland Restoration Program Clean Water Management Trust Fund Carteret Craven Electric Cooperative Jumping Run Creek Watershed Citizens Jumping Run Creek
- 16. Facts: 1)Shellfish closures occurring since 1979. 2) Imperviousness less than 5%. 3) Water moving through the system to shellfish bed within hours. 4) Bacterial loading has increased steadily through the years, while rainfall has stayed consistent.
- 17. J1 J2 J4 HY J1 J2 J4 HY J1 J2 J4 HY 0 50 100 150 Load(kg) Nonstorm Storm Loads from 9/5/99-6/5/00 NH3 NO2+3 PO4
- 18. J1 J2 J4 HY 0 5 10 15 20 25 30 TSSLoad(1,000kg) Nonstorm Storm Loads from 9/5/99-6/5/00
- 19. J1 J2 J4 HY 0 5 10 15 20 25 30 FecalColiform(1,000,000,000mpn) Nonstorm Storm Loads for 9/5/99-6/5/2000
- 20. Conclusions *Impervious area not adequate indicator of water quality threat. *Strategies to mitigate development need to address hydrologic alterations. *Bacterial source, not just location, needs to be known to properly manage.
- 21. Can Design and Planning Help? • Competing Values, Needs, and Interests.
- 22. Planning where development occurs really can matter • Wetlands • Headwater Streams • Link Open Space • Functioning Plant Communities • High Quality Waters • Recharge Areas • Buffers Zones
- 23. Need to plan and design development on a watershed basis • Reliance on end-of-pipe BMP technology will not achieve the 30% reduction standard for Nitrogen. • Development based on imperviousness alone can encourage sprawl. • New urban scenarios while providing opportunities to implement a variety of urban land use and sensitive area protection features are high density and can be high impact. • Source reduction approaches need to be assessed using watershed - based planning and design techniques to get the right uses in the right place.
- 24. Reduce Impervious Area: Reduce Road Widths -- Use one way streets, pull-off zones, back alleyways for utility infrastructure and parking, alternative materials. Reduce Parking Area -- Angled parking, narrower slots, lower allocation. Share Driveways -- Put more houses on each drive access. Reduce Paved Sidewalk Area -- Use one side only and alternative materials. Contain Stormwater On-Site Use Inverted Streets as Stormwater Collectors -- Direct to bio-filters. Invert Parking Islands to Collect Water. Direct Runoff from house gutters onto pervious areas. Reduce use of street curbing -- Use grassed or vegetative swales. Use Bioretention Areas and Rain Gardens Use Green Building Techniques Site Design Strategies
- 25. Site Design Strategies Incorporate wetlands, bioretention areas, buffers, open space into site plan.
- 26. Share Driveways -- Put more buildings / houses on each drive access. Direct Runoff from house gutters onto pervious areas. Use on-site bioretention. Minimize footprint--use taller buildings. Collect rainwater and reuse. Use pervious materials whenever possible. Structures-use Green Building Techniques
- 27. Carpenter Village Buffers Clustered Narrow / Short Streets Integrated Open Space Integrated Infrastructure Alleyway Access Varying density Integrated land uses Bioretention
- 28. Bioretention Case Study - Carpenter Village • Work with Developers and Town to identify suitable locations. – Ideal -- low area, good soils, water gathering slope form, dispersed in the watershed, part of city infrastructure. – Reality -- got existing open space, high grades, poor soils, only two locations in the watershed, located on private property (Developers responsibility).
- 29. Case Study - Carpenter Village • Worked with site engineers and Town staff to redesign stormwater infrastructure, streets, sidewalks, curbs. – Removed 17 storm drain inlets. • Two new inlets, hooked to stormwater infrastructure, with proper top and bottom elevation installed in location designated for bioretention. – Streets redesigned to direct water to swales and inyo bioretention. • Road Grades • Sidewalk Contiguity • Flat curbs
- 30. Case Study- Carpenter Village
- 31. Case Study - Carpenter Village
- 32. Case Study - Carpenter Village
- 33. Case Study - Carpenter Village
- 34. Case Study - Carpenter Village
- 35. • Rainwater Harvesting - the collection and reuse of rainwater for non-potable applications. – Reduction in storm water runoff. – Increased opportunities for re-infiltration. – Conserve potable water. – Save money. Case Study- Residential Demonstration
- 39. Case Study- Residential Demonstration • If linked to city water and irrigation system (which increases ease of use). – Requires programmable timer. – Labeled non-potable lines. • If not, only normal plumbing and electrical codes apply.
- 40. Case Study- Residential Demonstration • Rain Garden as part of the landscape – Locate in low point of the landscape. – Grade remainder of landscape to drain to rain garden. – Use simple plastic inlet system. – Provide overflow outlet. – Plant with facultative vegetation.
- 47. Conclusions: •Effective solutions need a “Toolbox” approach using watershed based planning, low impact design, and green building implementation techniques. •Wetlands and riparian buffers are essential for habitat and water quality. •Recharge rates must be addressed by capturing storm water utilizing infiltration techniques, reapplication, and the preservation of recharge areas, open space. Water quality protection can happen when hydrologic functionality of the watershed is maintained, pollutant load (including storm hydrology) is minimized.
- 48. More Conclusions! • Positive results can be achieved when there cooperation between towns to develop management strategies on a watershed basis. • Within that context, the good development work can be done if designed using multi-disciplinary teams that include architects, landscape architects, biologists, soil scientists, ecologists, botanists, and, yes, even engineers.